Electrical devices of various types may be cooled during operation by cooling chambers which are bonded directly to the electrical device and provide for the circulation of a cooling liquid. One type of an electrical device may be a semiconductor component such as a thyristor or silicon controlled rectifier which is cooled by a pair of cooling chambers fixed to the opposed major surfaces of the wafer forming the semiconductor portion of the device. Such cooling chambers provide for the circulation of a cooling liquid, as a heat pipe, or a cooling jacket or manifold for forced circulation of the cooling liquid. A semiconductor device of this type is described in detail in U.S. Pat. No. 3,739,235 issued to Sebastian William Kessler, Jr. on June 12, 1973. The semiconductor wafer of the type described in the patent has a conductive cathode electrode coating on one major surface of the wafer and a conductive anode electrode coating on the opposite major surface of the wafer to which the cooling chambers in the form of heat pipes are attached.
The cooling structure may consist principally of a hermetically closed metal chamber having one portion bonded to one of the two major surfaces of the semiconductor device. An electrical connector terminal is fixed to a part of the metal chamber at a position spaced from the respective conductive anode or cathode coating of the semiconductor wafer. The terminal serves to connect the semiconductor device into the external working circuit. This particular arrangement utilizes the cooling chamber as the electrical lead to the respective anode or cathode coating on the opposed surfaces of the wafer.
When thyristors and rectifiers of the type described above are used in a circuit, currents as high as 20,000 amperes or more can be developed. The semiconductor device is frequently protected with a special fuse connected in series with it. However, such fuses are expensive and often cost as much as the semiconductor device itself. This, then, has led some manufacturers of equipment to question the economy of protecting a semiconductor device with a fuse which is as expensive. For this reason, many circuits are designed without any fuse protection of the circuit and equipment. When the thyristor or rectifier fails by a breakdown of the semiconductor wafer, the large flow of current through the device tends to melt the mass of metal in contact with the wafer so that it fuses together and the semiconductor wafer is shorted, thus allowing short circuit currents to surge through the circuit or equipment. With no fuse protecting the circuit, the equipment can be destroyed and much damage can result.